In a fuel injection rotary piston internal combustion engine of the kind described it is known (German AS No. 1201 608) for different quantities of fuel to be injected within the load range between idling and full load from a first injection nozzle mounted in the peripheral portion and a second nozzle mounted in the inlet port, in order to maintain a well-formed mixture permanently in particular in the region of the spark plug. However as in this arrangement both injection nozzles are permanently in action, despite the delivery of to some extent minimal quantities of fuel it cannot be avoided that under idling conditions and in the lower partial load range as well as after a cold start there is some depositing of fuel on the walls of the inlet port and in the working chambers. Such deposits of fuel can for example penetrate past the seal elements and, as a consequence, interfere with the functioning of these elements. However, this has a particularly disadvantageous effect in its influence on the quality of the exhaust gas. Moreover the fuel injection pump which is provided for metering the delivery of fuel, including the control means necessary for varying the delivery, represents a relatively high outlay in cost.
From U.S. Pat. No. 3,126,876 and German published Specification No. 1,751,205 it is known to mount an injection nozzle in the peripheral portion in the neighbourhood of an inlet port that opens into the side wall. As explained in the above mentioned U.S. specification this layout makes it possible to employ, instead of a fuel metering device that operates at high pressure, a more economical device which operates at low pressure. Furthermore it has been proposed in this U.S. Pat. No. 3,126,876 and also in German Pat. No. 1,751,205 to surround the injection orifice of the nozzle with at least one air opening so that the fuel that is injected can mix either with the combustion air introduced from atmosphere to this opening or with a combustion mixture, allowing one to obtain an improved mixture formation and a higher efficiency. As has been found in practice the advantage that can be obtained by this layout shows itself, however, only under idling and light load conditions whereas at high speeds and in the operating range extending above the lower part of the load range, as well as at full load, the time available is too short for adequate mixture formation.